Renamed the Test coverage: velocity+maintainability+reliability+predictability section to Velocity+maintainability+reliability+predictability — sometimes mere untangling of broken architecture and fixing it can also be important for those 4 things. #2737751 is an example of that. It's been haunting us for years. Time to fix it.

We didn't make as much progress as I'd hoped in some areas (serialization gaps), but we made far more progress in other areas (test coverage). But obviously we fixed tons of issues, many of them requiring fixes in other subsystems. We achieved roughly half of the top priorities!

Many of them were very difficult to land, requiring lots of consensus building, or requiring blockers to be solved that aren't listed here, often in other subsystems. Many of the ones that did not land are already well on their way, making it very likely that they will land in 8.5.